The present invention relates generally to signal processing circuits, and more particularly to an improvement of a signal processing circuit such as a circuit for electrically generating binaural signals, circuits for eliminating crosstalk with respect to the two ears of a human being at the time when binaural signals are converted into sound with speakers, and combinations of these circuits.
A so-called binaural system in which microphones are provided at the positions of the two ears of a dummy head having the shape of a human head to record the sounds respectively at the positions of the two ears, and the sounds obtained by reproducing these recorded sounds are respectively supplied to the headphone speakers for respective ears of a headphone set is known. By using this system, the listener can hear these sounds as though the position of the acoustic image were at the same position as that of the actual sound source.
In order to obtain this binaural signal, a dummy head must be used, heretofore. Accordingly, a signal processing circuit for obtaining signals substantially equivalent, electrically, to binaural signals from an ordinary monaural signals or respective channel signals of stereo signals was devised. By the use of this signal processing circuit, substantially binaural signals can be obtained without the use of a dummy head.
However, the transmission characteristic of a signal processing circuit of this type known heretofore has large dips at specific frequencies, and the signal components of these frequencies become missing.
Furthermore, when binaural signals are applied to speakers disposed at positions separated from the listener, and a reproduced acoustic field is formed, sounds which originally should have been introduced by headphones separately unto respective ears of the listener are heard by both ears. For this reason, crosstalks of sounds are produced with respect to the two ears. Accordingly, a circuit for processing signals in a manner such that crosstalk components are electrically cancelled was devised. In accordance with this signal processing circuit, when binaural signals are applied to speakers separated from the listener, it can be heard as sounds of a binaural system.
However, the transmission characteristic of a signal processing circuit of this character known heretofore exhibits high peaks at specific frequencies. This has given rise to the problem of the occurrence of distortion in signal components of the frequencies showing the peaks during the amplification of the output signal of this signal processing circuit with an amplifier.
Another signal processing circuit which has been devised is a combination of the above described two kinds of signal processing circuits. In this combined circuit, binaural signals obtained from monaural signals or respective channel signals of stereo signals are emitted as sound from speakers at positions separated from the listener, and the listener is thereby able to hear sounds in an acoustic field resembling the binaural system.
This signal processing circuit has a transmission characteristic which is a combination of the transmission characteristics of the above described two kinds of signal processing circuits. Then, since the frequencies of the dips of the above described two signal processing circuits and the peak frequencies are respectively different, this combined signal processing circuit has dips and peaks in its transmission characteristic. For this reason, this circuit has a combination of the drawbacks of the above described two signal processing circuits.